(Reuters) - Three people were killed when fighting erupted overnight in the Lebanese city of Tripoli between members of the Alawite minority loyal to Syrian President Bashar al-Assad and members of the Sunni majority, witnesses and security officials said.

Rocket-propelled grenades and automatic rifles were used in the fighting in an Alawite enclave and surrounding Sunni neighborhoods in the port city, 70 km (45 miles) north of Beirut.

"The clashes peaked at dawn. The sound of gunfire is still echoing in the city," a Lebanese security official said.

The Lebanese state news agency said a soldier hit by sniper fire was among those killed.

A statement from the army said two soldiers were also wounded and reinforcements were being sent to the city and that troops were "pursuing armed men to return the situation to normality."

Troops had deployed in an area separating the Alawite enclave from the rest of the city.

A Reuters correspondent in the city said sporadic fighting was also taking place between groups of armed Sunnis and the army near a main Sunni district, adding most of Tripoli´s main intersections were blocked by burnt tires.

The fighting underlines how sectarian tensions in Syria can spill over into neighboring Lebanon.

SIT-IN PROTEST

A small Alawite minority is concentrated in Tripoli, a conservative Sunni city where many residents have been enraged by the Syrian government´s crackdown on the 14-month revolt against 42 years of rule by the Assad family and their Alawite establishment.

Syria´s Sunni majority is at the forefront of the uprising against Assad, whose sect is an offshoot of Shi´ite Islam.

Lebanon´s government, headed by Najib Mikati, a wealthy former businessman and a personal friend of Assad´s, has been among the few worldwide supportive of the Syrian government during the crackdown.

Mikati, who is from Tripoli, met religious leaders in the city on Sunday in an attempt to diffuse the situation, before meeting President Michel Suleiman in Beirut.

The two leaders then took part in an emergency meeting called by Suleiman for a security cabinet comprised of several ministers, army and security commanders.

The Syrian government has accused Islamist groups in Lebanon of backing insurgents fighting loyalist Syrian forces and of involvement in car bomb attacks on security targets.

For the past days, followers of a Sunni Islamist group in Tripoli have been staging a sit-in protest against the arrest of a man whom the authorities said had been in contact with an unnamed "terrorist organization."

The Islamists say the detainee, Shadi al-Moulawi, was arrested because he was helping Syrian refugees in Lebanon who had fled the crackdown across the border.

A statement by al-Jamaa al-Islamiya, an Islamist group in Tripoli, criticized the arrest of Moulawi as lacking due process. Police said he was arrested after thorough surveillance.

Syrian troops withdrew from Lebanon under international pressure in 2005 after a 29-year presence, but Assad retains significant influence in the country through his main ally, the Shi´ite guerrilla group Hezbollah, the only Lebanese party that has an officially approved arsenal of weapons. (Additional reporting by Laila Bassam; Editing by Kevin Liffey and Janet Lawrence) (© Thomson Reuters 2012. 05/13/12)